During the "Prologue - Barricade" mission, where you must destroy a gate by using a ballista, drop down the wall to a series of scaffolding then reach the ground. Fight several soldiers from the rebellion group and make your way to the guarded ballista. Kill the enemies and clear the square, then go further back from the ballista and look to your right, beside a house. You will find a dead man dressed in a white robe with a red belt laying face down on top of a broken hay wagon (a reference to Altair Ibnu La Ahad). Look up to see a wooden ledge with a bird, which is where an assassin would usually survey the surroundings (synchronize) and perform the leap of faith. Geralt will say "I guess they never learn".

You can also get a hidden ability named "Assassin" that gives a damage bonus on the attack that lands on enemy's back, This is a reference to the back stab assassination in Assassin's Creed.